An update on effects of ionizing radiation exposure on the eye

Abstract

The International Commission on Radiological Protection (ICRP) has considered for over 60 years that the lens of the eye is among the most radiosensitive tissues, and has recommended dose limits for the lens to prevent occurrence of vision impairing cataracts (VICs). Epidemiological evidence that doses much lower than previously thought produce cataracts led ICRP to recommend reducing dose threshold for VICs and reducing an occupational equivalent dose limit for the lens in 2011, when only a single threshold of 0.5 Gy was recommended. On the basis of epidemiological evidence, ICRP assumed progression of minor opacities into VICs and no dose rate effect. This contrasts with previously recommended separate thresholds for minor opacities and VICs, and for different exposure scenarios. Progression was assumed based on similar risks of cataracts and cataract surgery in Japanese atomic bomb survivors. The absence of dose rate effect derived from the observed similar thresholds for protracted exposures in Chernobyl cleanup workers and in atomic bomb survivors. Since 2011, there has been an increasing body of epidemiological evidence relating to cataracts and other ocular diseases (i.e. glaucoma and macular degeneration), particularly at low doses and low dose rates. This review paper gives an overview of the scientific basis of the 2011 ICRP recommendation, discusses the plausibility of these two assumptions in the light of emerging scientific evidence, and considers the radiosensitivity of the lens among ocular structures.

Estimation of planning organ at risk volumes for ocular structures in dogs undergoing three‐dimensional image‐guided periocular radiotherapy with rigid bite block immobilization

“…A PRV of the lens has already been established in dogs 6 . The lens is exclusively sensitive already to low doses of radiation and cataract formation can lead to loss of vision 2,35 . Cataract formation is, however, a non‐life‐threatening disease and can be treated with phacoemulsification surgery to restore vision 36 .…”

Pharmacological management of ionizing radiation injuries: current and prospective agents and targeted organ systems

“…On the basis of epidemiological evidence, it was assumed that the progression of opacities into vision-impairing cataracts had no dose rate effect. The above recommendations are based on epidemiological support since there are a small number of studies providing explicit biological, mechanistic evidence at doses <2 Gy [144,145].…”

Etiology of posterior subcapsular cataracts based on a review of risk factors including aging, diabetes, and ionizing radiation

“…Retinal DNA damage may be caused by mitochondrial oxidative stress in experimental autoimmune uveitis (Nguyen and Rao 2010). Ocular diseases (i.e., diabetic retinopathy, retinal arteriolosclerosis, retinal degeneration and glaucoma), including fibrotic eye diseases, were reported in systemic inflammation-prone atomic bomb survivors exposed to a mean dose of $0.5 Gy of mainly low-LET IR (Minamoto et al 2004;Hamada et al 2019). However, even low doses of high-LET, high-charge, high-energy ionsa unique feature of galactic cosmic rays affect the retinal vasculature, causing apoptosis of retinal endothelial cells in mice (Mao et al 2018).…”

“…Barnard et al (2019) recently found that murine LECs display an inverse dose-rate response, at doses 0.5-2.0 Gy, in terms of DNA damage signaling. Further investigation into the source of this observed response and the implications for the lens is required (Hamada et al 2019).…”

“…This review identifies several areas where further research would be beneficial in understanding IR-induced cataractogenesis. While an increasing number of epidemiological studies show cataracts are linked to a wide range of IR doses at different dose rates, the progressive nature of radiation cataractogenesis at low dose, and low dose rates remains largely unclear (Hamada et al 2019). There is a paucity of experimental IR data on age-acceleration, free-radical damage to lenticular proteins and lipids (Uwineza et al 2019).…”